The MEMS technology, in which semiconductor manufacturing process technologies are incorporated with mechanically machining technologies and/or material technology to realize a system having a fine three-dimensional structure on a semiconductor substrate, can be applied to a wide variety of fields. Applications of semiconductor sensor devices manufactured by the MEMS technology to detections of physical quantities, such as acceleration, angular velocity, pressure, in fields of automobiles, aero planes, mobile terminal devices and toys, particularly attract attention from people.
These semiconductor sensor devices have a special feature in having a movable part formed by the MEMS technology. They detect displacement of the movable part by change in resistance of piezo-resistors or electro-static capacitance and process the detected data to measure the acceleration, the angular velocity, the pressure and the like. Patent documents 1 through 3 disclose acceleration sensor devices, Patent documents 4 through 6 disclose angular velocity sensor devices, and Patent documents 7 and 8 disclose pressure sensor devices.
The acceleration sensor of Patent document 1 is schematically shown in FIG. 14, and will be briefly described below, referring to the figure. A semiconductor sensor device will be explained as an acceleration sensor device, unless otherwise specified. And, details in structures of a semiconductor sensor chip for the semiconductor sensor device may be omitted from description since they are similar to those of Patent documents 1 through 8. A three-axis semiconductor acceleration sensor having a movable part manufactured by the MEMS technology is shown in an exploded perspective view of FIG. 14A. In the three-axis semiconductor acceleration sensor 10h, an acceleration sensor chip 20h and an IC regulation plate 30h are bonded by adhesive, such as resin, with a predetermined distance between them in a case 71h. Chip terminals 24h of the acceleration sensor chip 20h are connected by electric wires 51h to terminals 34h of the IC regulation plate, and the terminals 34h of the IC regulation plate are connected by electric wires 51h to case terminals 74h, and sensor signals are taken out from outer terminals 75h. A case lid 72h is fixed on the case 71h by adhesive. FIG. 14B is a plan view of the acceleration sensor chip 20h viewed from a top of the sensor. In the acceleration sensor chip 20h, a three-axis semiconductor sensor element 20h′ and the chip terminals 24h are provided. The three-axis semiconductor sensor element 20h′ is composed of a frame 27h, a weight 26h and pairs of beams 25h, and the weight 26h is held in a center of the frame 27h by two pairs of beams 25h. On the beams 25h, some piezo-resistors are formed. X-axis piezo-resistors 21h and Z-axis piezo-resistors 21h′ are on one pair of beams, and Y-axis piezo-resistors 21h″ are on the other pair of beams.
In the three-axis semiconductor acceleration sensor 10h shown in FIG. 14, the case 71h and the case lid 72h are made of ceramic, such as alumina. Since there is a limit to make the thickness of the case 71h and the case lid 72h thinner because they are made of ceramic, it is difficult to make them smaller-sized but also lighter. Since the case terminals 74h and the outer terminals 75h are formed on the ceramic case 71h and they are connected through a ceramic, the ceramic case becomes high in manufacturing cost, and it has been difficult to realize a low-priced acceleration sensor as long as a ceramic case is used. Since the case lid 72h is bonded to the case 71h with adhesive resin to air-tighten them, they tend to be less air-tight due to an environmental change because resin is used.
A structure with an improved air-tightness is described in Patent document 9. As shown in FIG. 15A, a semiconductor sensor assembled substrate 4i is constituted of a semiconductor sensor substrate 2i having a number of semiconductor sensor chips 20i manufactured by an MEMS technology, and cap substrates 3i, 3i′, which have a number of cap chips 30i, 30i′ formed, bonded on a top surface and a bottom surface of the semiconductor sensor substrate 2i. Movable parts of the semiconductor sensor chips 20i are air-tightened by the upper and lower cap chips 30i, 30i′. By slicing the semiconductor sensor assembled substrate 4i along cutting lines 90i, 90i′ shown by dot-chain lines by a diamond cutting wheel, a semiconductor sensor assembly 40i shown in FIG. 15B is prepared. By restricting a sealed portion to the movable part of the semiconductor sensor chip 20i, it is easy to air-tighten. As shown in FIG. 15C, the semiconductor sensor assembly 40i is bonded to an inner bottom of a case 71i, and a case lid 72i is bonded to a top side of the case 71i to complete a semiconductor sensor device 10i. However, such a semiconductor sensor device enveloped in a case has been difficult to reduce its size and manufacturing cost.
A semiconductor sensor device, in which a semiconductor sensor assembly is covered with resin by applying a resin sealing technology of semiconductor as shown in Patent document 10, has started to be used in practice. FIG. 15D depicts an example of such a semiconductor sensor device 10j in which the semiconductor sensor assembly 40j is sealed with resin. By thinning a molding resin 70j to the extent that the semiconductor sensor assembly 40j and electric wires 51j are not directly exposed to outer atmosphere, miniaturizing and lightening the semiconductor sensor device can be realized. A bonding process of a case that was necessary for the semiconductor sensor device 10i of FIG. 15C is not required in the resin-sealed semiconductor sensor device 10j of FIG. 15D, and its manufacturing cost can be reduced.
Patent document 1:JP 2006-133123 APatent document 2:JP Hei 08-233851 APatent document 3:JP Hei 11-160348 APatent document 4:JP 2006-175554 APatent document 5:JP 2003-194545 APatent document 6:JP 2005-524077 WPatent document 7:JP 2004-132947 APatent document 8:JP Hei 10-098201 APatent document 9:JP Hei 03-002535 APatent document 10:JP Hei 10-170380 A